codice:
<html>

  <head>
    <style type="text/css">
    <!--

      table.maincontainer {
        width: 600px;
        text-align: center;
        vertical-align: middle;
      }

      td.segment {
        background-color: #777699;
        color: #000000;
      }

      td.seg_a {
        background-color: #336699;
        color: #000000;
        height: 100px;
      }

      td.seg_b {
        background-color: #ffcc00;
        color: #000000;
        height: 100px;
      }

      td.seg_c {
        background-color: #cc6600;
        color: #000000;
        height: 100px;
      }

    //-->
    </style>
  </head>

  <body>

    <table align="center" border="1" cellspacing="0" class="maincontainer">
      <tr>
        <td colspan="3" class="segment">NUOVA TABELLA A</td>
      </tr>
      <tr>
        <td class="seg_a"><h1>CELLA 1A</h1></td>
        <td class="seg_b"><h1>CELLA 2A</h1></td>
        <td class="seg_c"><h1>CELLA 3A</h1></td>
      </tr>
      <tr>
        <td class="seg_a"><h1>CELLA 1B</h1></td>
        <td class="seg_b"><h1>CELLA 2B</h1></td>
        <td class="seg_c"><h1>CELLA 3B</h1></td>
      </tr>
      <tr>
        <td colspan="3" class="segment">NUOVA TABELLA B</td>
      </tr>
    </table>

  </body>

</html>